Lisp: Notes on its Past and Future (1980) (www-formal.stanford.edu)
175 points by birdculture 17 hours ago
vindarel 13 hours ago
Old Lisp posts are cool, then if you want a refresher of what's happening in the CL ecosystem (tools, libraries, compilers…) here's an overview of the last two years (shameless plug): https://lisp-journey.gitlab.io/blog/these-years-in-common-li... and very cool new projects appeared in 2025.
labrador 17 hours ago
It occurred to me this morning that I should learn Clojure instead of Rust for non-lowlevel code because Clojure solves the same problems Rust solves in a much simpler way. I'm a fan of Clojure author Rich Hickey's "Simple Made Easy" talk but otherwise don't know either language in detail and need to do more research.
beders 11 hours ago
The Clojure (or any Lisp) journey is very different, not because of the language per se, but because of the developer experience.
In Clojure, there's no appreciable compilation time. During my work week I barely, if ever, restart the application I'm working on: I'm working inside of it via a REPL connection.
It's an entirely different ball game and if you just compare language features you are missing out on an incredible interactive coding experience.
labrador 8 hours ago
Does it scroll? Because I like to scroll around when thinking about my program. I always imagine Lips REPL ppl saying they keep the entire program in their head but that can't be right. That's doing things the hard way.
weikju 7 hours ago
skydhash 6 hours ago
andreicap 4 hours ago
Can confirm! Once I started doing this (now mainly with iPython interactive in VSCode) my output speed increased dramatically
chamomeal 9 hours ago
As an anecdote, about a year ago I realized I was not having that much fun learning rust. Randomly landed on clojure instead and have absolutely loved it.
Particularly as a noob, babashka is SUCH a good way to learn the language. I’ve written myself all sorts of fun utilities with babashka and have learned so much clojure along the way. Even got my coworkers to use my bb scripts!
lucasoshiro 16 hours ago
> Clojure solves the same problems Rust solves in a much simpler way
I'm curious about that, can you elaborate? I'm a beginner in Clojure and I only know a few concepts about Rust, but it seems to me that they solve (at least, currently) very different problems...
I only saw Rust being used in places where C or C++ would be used in the past (Linux kernel, CLI apps, desktop apps), while I only saw Clojure being used as a modern and functional Java and JS replacement.
Not to mention how different they are as languages (static vs dynamic typing, native vs jvm, borrow checker vs garbage collection)
Zambyte 15 hours ago
The main problem that Rust tries to solve, and that functional programming (which Clojure heavily leans into) solves, is avoiding shared mutable state, which leads to data races and (potentially subtly) wrong concurrent programs. Functional programming avoids shared mutable state by avoiding mutable state. Operations are only represented as transformations instead of mutations. Other languages like Erlang / Elixir use message passing techniques like the Actor Model to avoid shared mutability. Instead of avoiding mutability, like in functional programming, in the Actor Model you avoid sharing, by instead sending messages around.
Rust is interesting because it solves the problem of shared mutable state, while allowing sharing, and allowing mutability, just not at the same time. State can be mutated until it is shared. While it is shared, it cannot be mutated. This is the goal of the ownership system in Rust.
SkiFire13 6 hours ago
codesnik 3 hours ago
labrador 16 hours ago
One thing that jumped out at me is you don't need Rust's borrow checker to prevent thread race conditions because data in Clojure is immutable. That's a huge simplification over Rust. What I hear mostly about Rust is complaints about the borrow checker. I wrote a simple Rust utility and found it frustrating. But again, don't take my word for it because I don't know either language.
asa400 12 hours ago
bmitc 14 hours ago
jimbokun 12 hours ago
This the “non-low level” code qualification.
funkaster 10 hours ago
I would recommend taking a look at some of the schemes. In particular I've been having tons of fun with CHICKEN: https://call-cc.org/ - the fact that it compiles to C and can generate binaries is a great plus.
calgoo 2 hours ago
I have been enjoying Chez scheme these last few weeks, and having an LLM has helped me when i have missing libraries. The ability to just wrap a C library and statically link everything into a single binary has been really nice too!
kragen 12 hours ago
How does Clojure do on McCarthy's desiderata from this paper, as you see it?
armitron 16 hours ago
Clojure is a niche language that (for realistic purposes) is still tied to a single platform, the JVM, which (Clojure, not the JVM) looks more dead with every passing year. It never became popular and it's been steadily losing users. It's also not as general purpose as Common Lisp (ie. not suited for system or lowlevel programming).
If you're going to learn a niche Lisp, you might as well learn Common Lisp or Scheme which have well-specified standards, have stood the test of time and will still be around for decades to come.
kloud 16 hours ago
Although niche, things are pretty lively in the community. Among other things this year great progress was made on Jank, the native LLVM-based implementation with seamless low-level C++ interop. As part of that work a test suite is being created [0] and now includes runners for all of the major implementations to compare compatibility, next best thing besides a formal specification.
mpenet 16 hours ago
Clojure will be around as long as the jvm. It’s mostly done at the core level, most updates are to leverage new host features nowadays. The rest is happily provided at the library level by the community (which is still very prolific).
And it’s not tied to the jvm per say, look at clojurescript (and derivatives) or the upcoming jank.
It’s far from dead. As much as I like CL, the ecosystem is a bit of a desert compared to the jvm.
labrador 8 hours ago
kleiba 16 hours ago
kragen 16 hours ago
chamomeal 15 hours ago
JVM is very much not dead even slightly. They just released virtual threads, which are ridiculously awesome. Also it's not tied to a single platform, clojurescript lets you write clojure in browsers and on node.js, and babashka lets you use clojure in a scripting environment via a single executable
galaxyLogic 12 hours ago
lycopodiopsida 16 hours ago
I prefer CL, but… clojure at least has some commercial usage and is by far the most successful of current lisps, if we do not count elisp.
vindarel 10 hours ago
lucyjojo 10 hours ago
Clojure is not going anywhere anytime soon.
It sees plenty use as Clojure/Clojurescript and Babashka. (and other niche variants). Jank is shaping up to be real nice too.
labrador 16 hours ago
I don't care if it's niche if it solves my problems and gets the job done faster.
bitwize 16 hours ago
The JVM has suffered a fate worse than death: it's become so wildly successful that it's boring. So much enterprise shit runs on Java that it has sort of faded into the background noise of civilization and, like the System/360 (now Z/OS) before it, doesn't grab headlines anymore.
gleenn 14 hours ago
cmrdporcupine 16 hours ago
I frankly miss the JVM. I work almost exclusively in Rust these days and haven't worked in Java or Scala since 15 years ago, and I do prefer working closer to the metal.... But... The JVM is an amazing mature runtime with a boatload of tooling. JMX, which has been there since almost the beginning, is the kind of thing missing from almost everything other managed runtime I've worked with.
The amount of R&D that has gone into making it execute with good performance, and its overall stability...
Yeah, it's got the curse of being boring.
I do think it is perhaps unfortunate that Clojure is tied so heavily to the JVM, because I actually don't think it gains much from that ecosystem... but it's a product of the time it was first written.
Actually hell. I'm between jobs, I like Lisp, and I miss the JVM. I've never worked in Clojure, but does anybody want to hire me to work in it? :-)
asa400 12 hours ago
lenkite 16 hours ago
> the JVM, which looks more dead with every passing year.
Lol, only dying/dead in the febrile imagination of some HN commenters. The JVM has had some of the most explosive feature activity in the last several years. Java had several million greenfield projects in 2024-25 - among the top 6 greenfield programming languages according to the Github Octoverse.
AnimalMuppet 13 hours ago
You're saying that Clojure is looking more dead, so you suggest... Common Lisp? That looks considerably more dead than Clojure.
tjr 9 hours ago
swatson741 6 hours ago
We know in hindsight that lisp became most useful for representing computation, but what ever happened to AI? McCarthy says it's characteristic of LISP. SICP also mentions AI as being fundamental to lisp at the beginning of the book. Norvig & Russel used Common Lisp for the first edition of their book. But, then what happened? Why did it just disappear for no reason?
rahen 12 minutes ago
Lisp didn’t really disappear, symbolic AI did.
Lisp was ideal for reasoning systems, its homoiconic and meta-programmable nature is perfect for manipulating symbolic structures and logic. But when AI shifted toward numerical learning with neural networks, tensors, and GPU computation, Lisp’s strengths mattered less, and Python became the new glue for C/CUDA libraries like NumPy, PyTorch and TensorFlow.
Still, nothing prevents Lisp from coming back. It would actually fit modern deep learning well if a "LispTorch" with a CUDA FFI existed. We would have macros for dynamic graph generation, functional composition of layers, symbolic inspection, interactive REPL exploration, automatic model rewriting etc.
We almost had it once: Yann LeCun’s SN (the first CNN) was built on a C core with a Lisp interpreter on top to define, develop and inspect the network. It eventually evolved into Lush, essentially "Lisp for neural networks", which in turn inspired Torch and later PyTorch.
https://x.com/ylecun/status/1944504502260003296?lang=en
So Lisp didn't die in AI, it's just waiting for the right people to realize its potential for modern neural networks and bring it back.
sjamaan 5 hours ago
The AI winter happened. And the AI they talk about is classical, symbolic AI where you try to explicitly represent knowledge inside the computer. The new LLM stuff is all neural networks, and those benefit more from fast low-level vector implementations than high-level ease of symbolic manipulation.
So modern AI is all mostly C or even Fortran, often driven from something more pedestrian, like Python.
noam_k 4 hours ago
I'm not sure what exactly you're referring to, but one avenue to implement AI is genetic programming, where programs are manipulated to reach a goal.
Lisp languages are great for these manipulations, since the AST being manipulated is the same data structure (a list) as everything else. In other words, genetic programming can lean into Lisp's "code is data" paradigm.
As others mentioned, today everything is based on neural networks, so people aren't learning these other techniques.
swatson741 3 hours ago
I'm referring to the fundamental idea in AI of knowledge representation. Lisp is ideal for chapters 1 through 4 of AIMA, and TensorFlow has shown that NN can be solved well with a domain specific language which lisp is known to be great for.
In fact, the first edition of AIMA even had a NN and Perceptron implementation in Common Lisp. (https://github.com/aimacode/aima-lisp/blob/master/learning/a...)
g9yuayon 11 hours ago
I'm curious why Lisp didn't gain mass popularity despite its advantages. In fact, I was wondering if it's popularity has event decreased in the past decade or so. I remember in the 2000s and even early 2010s, there were active discussion on Clojure, Scheme, and functional/logic programming in general. There seems much less discussion or usage nowadays. One theory is that popular languages have absorbed many features of functional programming, so the mainstream programmers do not feel the need to switch. My pet theory is that many of us mortals get the productivity boost from the ecosystem, in particular powerful libraries and frameworks. Given that, the amazing features of lisp, such as its s-expression, may not be powerful enough to sway users to switch.
lucasoshiro 20 minutes ago
Clojure seems to be pretty strong. At least here in Brazil, several companies here use it as their main programming language
kragen 8 hours ago
Lisp has disadvantages too. I wrote about some of them in https://paulgraham.com/redund.html.
vindarel 2 minutes ago
Is it the right link? "Lisp" is mentioned once, in a good way. It's an old post too, it mentions Emacs' ilisp mode, which is the now unused ancestor of Slime.
originHarbor1 7 hours ago
It’s cool how people keep finding new joy in old ideas like Lisp. Shows that good design never really dies.
kloud 16 hours ago
> It seems to me that LISP will probably be superseded for many purposes by a language that does to LISP what LISP does to machine language. Namely it will be a higher level language than LISP that, like LISP and machine language, can refer to its own programs. (However, a higher level language than LISP might have such a large declarative component that its texts may not correspond to programs. If what replaces the interpreter is smart enough, then the text written by a user will be more like a declarative description of the facts about a goal and the means available for attaining it than a program per se).
Pretty accurate foresight in 1980, in the "Mysteries and other Matters" section McCarthy predicting declarative textual description replacing lisp as a higher-level programming language, basically describing todays LLMs and agentic coding.
labrador 15 hours ago
That is remarkable foresight. I've had Google Gemini take a Dart program it wrote for me and had it convert it to TypeScript while adding some additional requirements - so declarative programming and treating code as data
AnimalMuppet 13 hours ago
> Pretty accurate foresight in 1980, in the "Mysteries and other Matters" section McCarthy predicting declarative textual description replacing lisp as a higher-level programming language, basically describing todays LLMs and agentic coding.
To me, that sounds more like Prolog than agentic coding.
bmitc 14 hours ago
I don't see the connection to LLMs. With LLMs, you have a highly non-deterministic system that is also highly probable to be incorrect.
It seems like a stretch to say that's what McCarthy was thinking about regarding declarative facts and goals driving a program.
goatlover 16 hours ago
How many people are using LLMs to replace coding in Lisp? What code are these former Lispers producing with LLM Agents?
I understand what you're trying to say, but I don't think LLMs were created as some replacement for Lisp. I don't think they've replaced any programming language, but they do help quite a bit with autogeneration of Python & Javascript in particular.
mmmm2 15 hours ago
LLMs seem better suited to help with the Tower of Babel we've created for ourselves: aws commands, Terraform modules, Java libraries, Javascript/React, obscure shell commands, etc.
atgreen 15 hours ago
I've been having a great time generating Common Lisp code with LLMs. eg. https://github.com/atgreen/cl-tuition , https://github.com/atgreen/ctfg , etc.
seg_lol 14 hours ago
kloud 15 hours ago
The strength of Lisps is in ability to define DSLs and then concisely express solutions for problems in that domain. Arguably no other programming language was able to exceed or even match that power until now.
The math behind transformers is deterministic, so LLMs could be treated as compilers (putting aside intentionally adding temperature and non-determinism due to current internal GPU scheduling). In the future I imagine we could be able to declare a dependency on a model, hash its weights in a lockfile and the prompt/spec itself will be the code, which corresponds to that insight.
galaxyLogic 12 hours ago
g_host56 13 hours ago
nice, I was hacking common lisp this weekend.
Also this video was interesting, Oral History of John McCarthy: https://www.youtube.com/watch?v=KuU82i3hi8c&t=1564s
sema4hacker 15 hours ago
I think when programmers are introduced to languages, most grok procedural ones easier than functional ones, hence Lisp and its derivatives have struggled in popularity for decades.
PessimalDecimal 13 hours ago
I have been thinking about the reason why Lisps aren't more popular today. I'm not sure yours is the right reason though. It seems like the statement you make would be no more true today than in the 80s, when Lisp was much more popular.
Ultimately I think it might just be fads. Object oriented programming came along at the same time as the web, when the demand for programmers grew dramatically. That may have crystallized OO and imperative languages as the "default" style. Would be interesting to see the alternate universe where JavaScript actually was a Lisp.
galaxyLogic 12 hours ago
JavaScript has been called "Lisp in C's clothing". JavaScript is not a "pure" functional language but are any of the Lisps either? They might have immutability as the default. But I don't see why an Object-Oriented language could not have immutability as the default as well?
sema4hacker 12 hours ago
In the 80's Lisp was already over 20 years old.
shawn_w 15 hours ago
Common Lisp supports both styles. Shoot, it probably favors procedural over functional a bit.
galaxyLogic 12 hours ago
From what I've understood about Haskell is that it allows you to divide your program into parts which are either pure functional, or mutable. That is great when you read the program, you can know that what you are reading now is immutable, whereas in the some other well designated parts it is mutable.
But with Lisps isn't it the case that statement 1 can be immutable while the next statement 2 is mutable? In other words it mixes mutable and immutable calls into the same program-file without really isolating them from each other in any way. And that means if one part of the program is "impure", so is all of it. You can't isolate those parts except by following a convention, but conventions are not something that it enforces. And you can't know which parts of your program are pure except by reading the code-statements in detail. Am I right?
wild_egg 11 hours ago
shawn_w 11 hours ago
wild_egg 13 hours ago
It supports basically all styles which makes it wonderfully useful in whatever domain you happen to find yourself in.
keithnz 8 hours ago
Back in the 80s we had logo, that was super popular and a common way a lot of people (kids) learned programming, the birth of turtle graphics! That repl way of programming and getting visual results was really good. I think the biggest problem was that none of those languages were the languages for making games.